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Likurg_2 [28]
3 years ago
13

A study indicates that teenagers spend an average of 112 minutes watching videos on their smartphones per week. Assume the distr

ibution is normal, with a standard deviation of 12 minutes. What is the probability that a teenager spends less than 90 minutes watching videos on their phone per week
Mathematics
1 answer:
lara31 [8.8K]3 years ago
3 0

Answer:

0.0336 = 3.36% probability that a teenager spends less than 90 minutes watching videos on their phone per week.

Step-by-step explanation:

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean \mu and standard deviation \sigma, the z-score of a measure X is given by:

Z = \frac{X - \mu}{\sigma}

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

A study indicates that teenagers spend an average of 112 minutes watching videos on their smartphones per week. Assume the distribution is normal, with a standard deviation of 12 minutes.

This means that \mu = 112, \sigma = 12

What is the probability that a teenager spends less than 90 minutes watching videos on their phone per week?

This is the p-value of Z when X = 90. So

Z = \frac{X - \mu}{\sigma}

Z = \frac{90 - 112}{12}

Z = -1.83

Z = -1.83 has a p-value of 0.0336

0.0336 = 3.36% probability that a teenager spends less than 90 minutes watching videos on their phone per week.

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A bus has less than 42 seats. If 36 seats are already occupied, write an
Fudgin [204]

Answer:

B

Step-by-step explanation:

A x - 36 <42 is wrong because its saying how many can be added

B x +36 < 42 this one is most likely correct because its displays x as how many can be added

C x - 36 > 42 this is wrong because the bus has less than 42 seats

D x + 36 >57 like i said cant be over 42

8 0
3 years ago
A 100 gallon tank initially contains 100 gallons of sugar water at a concentration of 0.25 pounds of sugar per gallon suppose th
Vsevolod [243]

At the start, the tank contains

(0.25 lb/gal) * (100 gal) = 25 lb

of sugar. Let S(t) be the amount of sugar in the tank at time t. Then S(0)=25.

Sugar is added to the tank at a rate of <em>P</em> lb/min, and removed at a rate of

\left(1\frac{\rm gal}{\rm min}\right)\left(\dfrac{S(t)}{100}\dfrac{\rm lb}{\rm gal}\right)=\dfrac{S(t)}{100}\dfrac{\rm lb}{\rm min}

and so the amount of sugar in the tank changes at a net rate according to the separable differential equation,

\dfrac{\mathrm dS}{\mathrm dt}=P-\dfrac S{100}

Separate variables, integrate, and solve for <em>S</em>.

\dfrac{\mathrm dS}{P-\frac S{100}}=\mathrm dt

\displaystyle\int\dfrac{\mathrm dS}{P-\frac S{100}}=\int\mathrm dt

-100\ln\left|P-\dfrac S{100}\right|=t+C

\ln\left|P-\dfrac S{100}\right|=-100t-100C=C-100t

P-\dfrac S{100}=e^{C-100t}=e^Ce^{-100t}=Ce^{-100t}

\dfrac S{100}=P-Ce^{-100t}

S(t)=100P-100Ce^{-100t}=100P-Ce^{-100t}

Use the initial value to solve for <em>C</em> :

S(0)=25\implies 25=100P-C\implies C=100P-25

\implies S(t)=100P-(100P-25)e^{-100t}

The solution is being drained at a constant rate of 1 gal/min; there will be 5 gal of solution remaining after time

1000\,\mathrm{gal}+\left(-1\dfrac{\rm gal}{\rm min}\right)t=5\,\mathrm{gal}\implies t=995\,\mathrm{min}

has passed. At this time, we want the tank to contain

(0.5 lb/gal) * (5 gal) = 2.5 lb

of sugar, so we pick <em>P</em> such that

S(995)=100P-(100P-25)e^{-99,500}=2.5\implies\boxed{P\approx0.025}

5 0
3 years ago
WILL MARK BRAINIEST!!!
Zarrin [17]
R^2/2(pi/180*D-sin(D)) is the formula so 6^2/2(pi/180*120-sin(120)) is the problem which comes to about 22cm^2
4 0
3 years ago
Read 2 more answers
Help on this thx for helping if you did
vichka [17]
To evaluate two fractions being divided, you must turn the right fraction into a reciprocal. That means you must put the bottom number at the top and then put the top number on the bottom (you’re basically switching them).

8/13 / 3/2

Now, once you turned the other number into a reciprocal, you multiply across. The top number times the other top number and do this to the bottom numbers, too.

8/13 * 3/2 = 24/26

You found the answer, 24/26. But as you can see, it’s not one of the choices. That’s because you need to simplify.

24/26 / 2/2 = 12/13

12/13 is your answer, or choice C!

I hope this helped. Comment below if you have any questions.
6 0
3 years ago
What is the answer ?
MrMuchimi
C is the correct answer
6 0
3 years ago
Read 2 more answers
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